The present invention relates generally to a modular fore-end rail assembly for firearms. More specifically, the present invention relates to a modular fore-end rail assembly for retrofitting a firearm that includes an upper hand guard portion, which is clamped around and supported by the barrel nut and a removable lower hand guard portion that is mounted onto the upper hand guard portion to fully surround the firearm barrel.
In the general field of combat and commercial weaponry, there is a broad range of accessories available for mounting onto standard firearms in order to upgrade the capability of these weapons. Of particular interest in the context of upgrade accessories is the M16/M4 weapon system that is typically utilized in military or combat settings. Generally, the M16/M4 weapon includes a lower receiver, an upper receiver, a butt stock extending rearwardly from the upper and lower receivers and a barrel that is attached to the front of the upper receiver and extends in a forward direction. Referring to FIGS. 1 and 2, an M16 weapon system is shown and generally illustrated at 10. As can be seen, the barrel 18 is attached to the front of the upper receiver 14 by inserting the rear end of the barrel into a barrel-receiving receptacle 20 at the front end of the upper receiver 14. A pin 22 on the barrel 18 aligns with a notch 24 in the barrel-receiving receptacle 20 to insure that the barrel 18 is properly aligned with the upper receiver 14 when the barrel is installed into the barrel-receiving receptacle 20. The barrel 18 is held in assembled relation with the upper receiver 14 by a barrel nut 26 that is threaded onto the outside surface of the barrel-receiving receptacle 20. In this manner, the barrel nut 26 is rigidly engaged with the barrel receiving receptacle 20 and the upper receiver 14 of the weapon 10, while also serving to retain the barrel 18 in its installed position. A “delta ring” 28 (FIG. 1) encircles the barrel nut 26 and provides a spring loaded ring for attachment and support of the M16/M4 standard hand guards (not shown) between the delta ring 28 and a forward receptor cap 32 mounted at the front end of the barrel 18. A gas tube 29 extends from the upper receiver 14 to the receptor cap 32 at the front end of the barrel 18. The standard hand guards, when installed, encircle and protect both the barrel 18 and gas tube 29.
Most new models of the M16/M4 weapons also include a dovetail rail interface 30 integrally formed along the top of the upper receiver 14. This interface rail 30 provides a convenient mounting point for many of the available accessories for use with the M16/M4 firearm such as scopes, sighting devices, lasers and directed fire devices. However, since this rail interface 30 extends only along the upper receiver 14 it is limited in length to the length of the upper receiver 14. The difficulty is that many military personnel have multiple sighting devices in addition to a variety of lighting devices, accessory handgrips, etc. that could also be attached to the weapon for enhanced use of the weapon. In view of the broad range of add on accessories, there is not enough space on the rail interface 30 provided on the upper receiver 14 to accommodate all of the accessories that the user may desire to use. Accordingly, there is a clear need for integration systems that include additional dovetail rail interfaces in order to support the wide variety of auxiliary equipment that is needed while also being able to withstand rigors of combat use and abuse.
While there have been many attempts in the prior art to provide additional dovetail rail interfaces, the difficulty found in most of the prior art interface rails is that they require support both on the receiver end as well as at the end of the barrel. As can be appreciated, by supporting one end of the interface rail on the barrel in this manner, additional weight and/or shocks are transferred into the barrel and more critically to the point of attachment between the barrel and the upper receiver. Such load transfer can adversely affect the alignment of the barrel with the upper receiver, which in turn interferes with the reliable function of the weapon.
To avoid transferring additional loads into the barrel of the firearm and avoid bending and “droop” along the longitudinal axis of the barrel that may be caused by excess weight near the front end of the barrel, the barrel must be isolated from the fore-end attachment. The benefits of mounting the fore-end attachment in a manner that isolates the barrel include the ability to prevent heat transfer from the barrel to the accessory devices mounted on the fore-end attachment as well as to provide a structure that will bear the weight of the accessories without transferring additional loads into the barrel.
Recognizing these benefits, there are numerous interface rail attachments in the prior art that have attempted to minimize the amount of weight carried by the barrel by attaching to both the upper receiver and the barrel. However in such configurations, the weight of any accessories mounted on the interface rail system is still partially carried by the front end of the barrel. There are other rail interface systems in the prior art that are supported directly from the upper receiver of the weapon and do not require any support from the gun barrel. However, many of these devices require removal and replacement of the original barrel nut with a modified barrel nut that includes a means for interfacing and supporting the rail. Other disadvantages include the fact that frequently these devices are formed as a unitary tubular assembly thereby preventing access to the barrel once the tubular assembly is installed.
Accordingly, there is a need for a modular fore-end rail assembly for mounting accessories to a firearm that supports the accessories without introducing loads or additional stresses into the barrel of the firearm. There is a further need for a modular fore-end rail assembly that can be mounted to a firearm that derives its structural support entirely from the upper receiver of the firearm while not requiring the replacement of modification of the existing barrel nut. Finally, there is a need for a modular fore-end rail assembly that provides an easily removable portion that allows access to the barrel of the firearm without having to remove the entire assembly from the firearm.